Positive displacement pump



J. C. RHODES ETAL POSITIVE DISPLACEMENT PUMP Filed Oct. 29, 1959 s 71:2.152 15E mmm. I v 1 mg N ,5 a v .3 k l .3 Q S Q E Q v t w R m fiQ \u wwmm, m a m n. n vw |||l|1|||||||I1I|I|||ILII7QAA n u..

Feb. 5, 1963 United States Patent 3,076,417 hOfllTlVE DESPEJACEMENT PUMPJoseph C. Rhodes, Park Forest, and John P. Segers, Crete, E1, assignorsto fitandard Oil Company, Chicago, 111., a corporation oi lindiana FiledOct. 29, 1959, Ser. No. 849,553 2 Claims. (61. 103-23tl) This inventionrelates to reciprocating, positive displacement pumps. In a moreparticular aspect it relates to a check valve assembly for a positivedisplacement pump.

On many occasions it is desirable to accurately and positively displacevapors, gases and liquids in combination or liquids of low vaporpressure from one space into another. In both instances the operabilityof the pump is affected and the efliciency reduced. The difliculty ofpumping liquids is increased where the net postive suction head (NPSH)of the fluid is insuflicient. The NPSH is the excess of pressure at thepump suction over the vapor pressure of the liquid. Where liquids mustbe pumped under such conditions an excessive pressure drop across theintake valve of the pump may cause the liquid to flash into a vapor onthe suction stroke of the pump. The result is an alternate compressionand expansion of the vapors and/ or gases, which reduces the pumpcapacity and negates the accuracy of displacement. Conventionalequipment is not suitable for such use because of the existence of largedead spaces at the end of the piston stroke and in the connections tothe exhaust valve, and because of the excessive pressure drop across thecheck valves.

One object of this invention is a pump which is capable of efiicientlypumping liquids, gases and vapors at a constant volumetric rate. Anotherobject is a pump which is capable of displacing such fluids from acontainer in which the fluid is enclosed at subatmospheric pressures orwhen the retaining pressure is less than the vapor pressure of theliquid to be pumped. A further object is such a pump which has a longlife, with a minimum of maintenance required. A more particular objectis such a pump having a minimum pressure drop across the intake valve.Another particular object is such a pump having no pressure drop acrossthe exhaust valve. Still another particular object is such a pump whichhas a minimum of dead space at the end of the piston exhaust stroke.Other objects will be apparent from the detailed description of thepreferred embodiment of the invention.

The above objects are attained in a reciprocating pump provided with amagnetic check valve on the intake stroke, with an exhaust valve adaptedto be mechinically unseated by the action of the piston or the fluidpressure produced within the cylinder during the exhaust stroke, andhaving a minimum volume between the end of the piston at the completionof the exhaust stroke and the exhaust valve ort.

FIGURE 1 is a schematic representation of the positive displacement pumpof the invention, and

, FIGURE 2 is a cross-section of the valve head and valve assembly, andFIGURE 3'is a cross-sectional end view of the valve head and valveassembly taken at line A-A, and FIGURE 4 is a plan view of the valvedisc employed in the valve assembly.

Referring to FIGURE 1 of the drawings, our improved positivedisplacement pump 16 is mounted on an appropriate base 11. The pump isprovided with a cylinder 12,

within which a piston 13 is mounted. A suitable linkage 14 connects to adriver 16 which imparts a reciprocating motion to the piston 13 by meansof a rack and pinion, cam or the like, so that the piston 13 slideswithin the cylinder 12. The driven end of the pump may be sealed againstloss of fluid within the cylinder by graphited pack- 3,075,417 PatentedFeb. 5, 1963 "ice ing or the like. The fluid end of the cylinder 12 isprovided with a valve head 17 which encloses the fluid, or outer, end ofthe cylinder. The valve head 17 is joined to the cylinder 12 preferablyby threaded engagement therewith. However, this joint may be of flangetype or other suitable construction. It is to be understood that thevalve head 17 is defined by that portion of the pump outboard from theend of the piston 13 at the completion of the exhaust stroke. The valvehead 17 is provided with an inlet conduit 18 which conducts the fluid tobe pumped from a reservoir 19 into the cylinder 12. Outlet conduits 21and 21a serve to conduct away the fluid discharged from the pump. Thepump discharge may be passed through only one discharge conduit,however, it has been found to be advantageous to provide two dischargeconduits. The upper discharge conduit 21 serves to carry away thedischarged vapors and gases, and the bottom conduit 21a carries away thedischarged liquids.

FIGURE 2 shows a cross-section of the preferred construction of thevalve head 17, the valve assembly 22, the piston 13 and the cylinder 12.The inlet conduit 13 passes the fluid to be pumped through a check valve23 through flow channels between the valve disc 3 1 and the check valvehousing, and through intake port 24 into the bore of the cylinder 12when the piston 13 is moved from the outer end of the cylinder towardsthe driven end of the cylinder to produce an intake stroke. When thepiston 13 is driven toward the outer (fluid) end of the cylinder 12 inthe exhaust stroke, the fluid contained in the cylinder is compressed.The amount of compression which occurs will depend upon the relativeamounts of liquid and vapors contained within the cylinder when theexhaust stroke is begun. As a result of this compression the pressure isbuilt up in the cylinder 12. A plunger 26 positioned within the valvehead 17 relieves the pressure within the cylinder 12 by compressing aspring 27 so that the plunger 26 moves and allows the fluid underpressure to be discharged from the cylinder 12. This discharge isconducted around the plunger 26 to the valve head 17 and is dischargedfrom the system through the pump outlet 28 and 28a. In the preferredform, the

' plunger 26 is provided with a plurality of raised members or ribs 26',as shown in FIGURE 3, spaced around the periphery of the plunger andextending radially from the plunger to provide flow channels between theplunger periphery and the inner wall of the valve head. The periphery ofthe plunger 26 or the inner wall of the valve head 17 is relieved toprovide flow channels between the plunger and the inner wallcommunicating with the bore of the cylinder 12 and the pump outlets 28and 28a. Near the end of the exhaust stroke the end of the piston 13mechanically unsea-ts the plunger 26 by pushing it from its seat on theshoulder 29 on the end of the cylinder 12. The plunger is displacedabout This mechanical unseating relieves the pressure in the cylinder 12and allows fluid to escape freely into valve head 17. Thus the effectivedead space is held to a minimum.

The check valve 23 preferably is mounted Within the plunger 26 and isprovided with an inlet port 20 for receiving fluid from conduit 13 andpassing it into the valve housing 37, and an outlet port 25. On thesuction stroke of the piston 13 fluid from conduit 18 passes into thevalve housing to cause the valve disc 31 to become unseated. As thevalve disc moves away from the valve seat 32, the incoming fluid passesaround the valve disc between it and the inner wall of the valvehousing. Flow channels may be provided between the valve disc and thewall of the housing my employing a valve disc having a plurality of ears31', as shown in FIGURE 4, extending radially from the disc and spacedaround its periphery so as to space the disc from the housing wall. Thefluid then passes from the valve housing by way of the outlet port 25,through the intake port 24 and into the bore of the pump cylinder.During the exhaust stroke the check valve closes to prevent the escapeof fluid after it has entered the pump. It is preferred to use amagnetic type check valve in order to obtain a minimum pressure dropacross the intake valve. It has been found that this type of valve opensupon a fraction of an ounce of pressure, i.e., about /2 ounce.Additionally, the magnetic check valve has a desirable snap open actionbecause of the decrease in strength of the magnetic field as the valvedisc 31 is unseated from the valve seat 32 and moves away from themagnet 33. In order to obtain a better seal, the valve seat 32 may beprovide with an ring of rubber or other material compatible with thefluid to be pumped. While we have described a magnetic check valve it isto be understood that the check valve may be a butterfly type, or ofanother type suitable for a specific use.

The plunger 26 covers the end of the cylinder bore and is seated againsta shoulder 29 provided at the end of the cylinder 12 and acts as theexhaust valve. The spring 27 maintains the plunger 26 in place andprevents the escape of fluid from the cylinder until the plunger 26 isunseated. It is advantageous to employ an outer 0 ring 34 on the face ofthe plunger 26 in order to provide a better seal. When the pressurewith-in the cylinder overcomes the force exerted on the plunger by thespring 27 this seal is broken and the fluid is discharged from thecylinder 12. In the event suflicient pressure is not built up to unseatthe plunger near the completion of the exhaust stroke the end of thepiston 13 mechanically unseats the plunger from the shoulder anddisplaces it about /3. This assures that the exhaust valve will be openso as to require no pressure drop, and also provides a minimum of deadspace between the end of the piston and the exhaust valve. In order toinsure that no fluid is allowed to pass in either direction through theintake port 24 a second inner 0 ring 36 is provided so that the end ofthe piston seals the entrance port when it contacts the plunger 26.

By mechanically unseating the plunger assembly which acts as an exhaustvalve the pressure of the dead space in the system is reduced to thepressure of the system into which the pump discharges. Only the smallopening behind the valve disc 31 and the intake port 24 are undercompression at the beginning of the intake stroke. If the system ispumping both liquid and gases this space is largely filled with liquidand does not significantly affeet the efliciency of the pump. By placingthe assembly so that the intake stroke is upward the entire dead spacemay be filled with liquid and the efiiciency would be substantially100%.

One of the advantages of the above described pump is that it combinesthe features obtainable in a pressure relieving exhaust valve with thoseof a mechanically relieving exhaust valve. That is, it is capable ofpumping from systems with greater intake than exhaust pressures, and thepressure of the dead space is reduced to that of the exhaust system atthe end of the exhaust stroke.

The inlet tubing 18 enters the valve head 17 and is rigidly. connectedto acheck valve housing 37 which is moved in the direction of thelongitudinal axis of the cylinder 12 when the plunger 26 is unseatedfrom the shouldder 29. In order to provide a seal where the inner tubing18 passes through the valve head 17 a flexible seal 38 is providedaround inner tubing 18. For this purpose it is preferred to use aflexible tubing such as neoprene which provides a snug fit over thetubing 18, and which forms a seal at its ends with the outer end of theplunger 26 and the inner wall of the valve head 17 through which thetubing 18 passes. In a preferred construction a spring guide 3 9 isplaced against this same wall encircling the inner tubing 18, andprovided with a spring guide 0 ring seal 41 adjacent to the wall of thevalve head 17. The spring guide is also provided with a cylindricalextension which fits inside of the spring 27 in order to support 4 andguide the spring. When this spring guide 39 is so used the outer end ofthe flexible seal 38 forms a seal therewith. Although the flexible seal38 has been so described it is to be understood that the same purposemay be accomplished by the use of a conventional stutling box andpacking, a bellows or other type of seals.

A pump constructed as in FIGURES 1 and 2 has satisfactorily displaced amixture of hydrocarbon gases, vapors and liquids from a chamber atsubatmospheric pressure at the rate of 40 ml. per minute of liquid andml. per minte of gases and vapors.

Having described our invention, what we claim is:

1. In a reciprocating piston pump adapted for pumping liquids, gases andvapors at a substantially constant rate, which pump is provided withvalve means for controlling the flow of fluid to and from the bore of acylinder of said pump, apparatus which comprises: a valve head memberpositioned to enclose the fluid end of said cylinder; plunger meansmovably positioned within said valve head member and at the outer end ofthe cylinder bore, said plunger means being provided with an intake portcommunicating with said cylinder bore, and further being provided with asurface covering the area of the cylinder bore which surface includes afirst outer seating surface adapted to engage in sealing contact withthe outer end of the cylinder, and a second inner seating surfacelocated within the periphery of said outer surface encircling saidintake port and adapted to engage in sealing contact with the end of thepiston; check valve means in flow communication with said intake port,said check valve means comprising a valve housing provided with inletand outlet ports communicating to permit a flow of fluid into and out ofsaid housing, a magnet rigidly mounted in said housing, a valve seatencompassing said outlet port and a magnetically responsive valve discmovably positioned in said housing between said check valve ports, whichvalve disc is attracted to said magnet and engages with said seat toclose said outlet port during the discharge stroke of said piston anddisengages from said seat under inlet fluid pressure influence greaterthan the attraction of said magnet to open said outlet port during theintake stroke of said piston, means adapted for maintaining said plungermeans in sealing contact with said cylinder bore during the intakestroke of said piston and responsive to pressure in said cylinder boreto permit movement of said plunger means away from the end of saidcylinder bore at a preselected pressure, conduit means for passing fluidto be pumped to said check valve inlet port, and fluid discharge conduitmeans communicating with said cylinder bore when said first outerseating surface of said plunger means is disengaged from said outer endof said cylinder during the discharge stroke of said piston.

2. In a reciprocating piston pump adapted for pumping liquids, gases andvapors at a substantially constant rate, which pump is provided withvalve means for controlling the flow of fluid to and from the bore of acylinder of said pump, apparatus which comprises: a valve headpositioned to enclose the outer end of said cylinder; a plunger movablypositioned within said valve head at the outer end of said cylinder boreand provided with a surface which is adapted to cover the area of saidcylinder bore, said surface being provided with an intake port, with afirst outer seating surface adapted to engage in sealing contact withthe outer end of said cylinder bore, and with a second inner seatingsurface adapted to engage in sealing contact with the end of saidpiston, said second inner seating surface being located within theperiphery of said outer seating surface and encircling said intake port;a check valve mounted in said plunger and comprised of a valve housingprovided with inlet and outlet ports, said outlet port communicatingwith said intake port, a magnet rigidly mounted in said housing, a valveseat encompassing said outlet port and a magnetically responsive valvedisc movably positioned in said housing between said check valve ports,which valve disc is attracted to said magnet and engages with said seatto close said outlet port during the discharge stroke of said piston anddisengages from said seat under fluid pressure influence greater than afraction of an ounce to open said outlet port during the intake strokeof said piston; a helical spring for maintaining said first outersurface of said plunger in said outer end of said cylinder bore duringthe intake stroke of said piston while permitting said plunger to moveaway from the outer end of said cylinder bore at a preselected pressurewithin said cylinder; an inlet conduit passing through a wall of saidvalve head and rigidly connected to said valve housing for passing fluidto be pumped to said check valve inlet port cylinder bore; sealing meansaround said inlet conduit adapted to provide a fluid tight seal betweensaid inlet conduit and said valve head; pump outlet means positioned insaid valve head; and flow channel means between the inner wall of saidvalve head and said plunger communicating said cylinder bore with saidpump outlet means when said first outer seating surface of said plungeris disengaged from said outer end of said cylinder bore during thedischarge stroke of said piston.

References Cited in the file of this patent UNITED STATES PATENTS737,809 Whitmaker Sept. 1, 1903 1,688,978 McCallum Oct. 23, 19282,599,898 Dalrymple June 10, 1952 2,646,071 Wagner July 21, 19532,708,944 Modine May 24, 1955 2,775,399 Robinson et a1 Dec. 25, 19562,894,526 Booth et a1. July 14, 1959 FOREIGN PATENTS 750,851 France June6, 1933

1. IN A RECIPROCATING PISTON PUMP ADAPTED FOR PUMPING LIQUIDS, GASES ANDVAPORS AT A SUBSTANTIALLY CONSTANT RATE, WHICH PUMP IS PROVIDED WITHVALVE MEANS FOR CONTROLLING THE FLOW OF FLUID TO AND FROM THE BORE OF ACYLINDER OF SAID PUMP, APPARATUS WHICH COMPRISES: A VALVE HEAD MEMBERPOSITIONED TO ENCLOSE THE FLUID END OF SAID CYLINDER; PLUNGER MEANSMOVABLY POSITIONED WITHIN SAID VALVE HEAD MEMBER AND AT THE OUTER END OFTHE CYLINDER BORE, SAID PLUNGER MEANS BEING PROVIDED WITH AN INTAKE PORTCOMMUNICATING WITH SAID CYLINDER BORE, AND FURTHER BEING PROVIDED WITH ASURFACE COVERING THE AREA OF THE CYLINDER BORE WHICH SURFACE INCLUDES AFIRST OUTER SEATING SURFACE ADAPTED TO ENGAGE IN SEALING CONTACT WITHTHE OUTER END OF THE CYLINDER, AND A SECOND INNER SEATING SURFACELOCATED WITHIN THE PERIPHERY OF SAID OUTER SURFACE ENCIRCLING SAIDINTAKE PORT AND ADAPTED TO ENGAGE IN SEALING CONTACT WITH THE END OF THEPISTON; CHECK VALVE MEANS IN FLOW COMMUNICATION WITH SAID INTAKE PORT,SAID CHECK VALVE MEANS COMPRISING A VALVE HOUSING PROVIDED WITH INLETAND OUTLET PORTS COMMUNICATING TO PERMIT A FLOW OF FLUID INTO AND OUT OFSAID HOUSING, A MAGNET RIGIDLY MOUNTED IN SAID HOUSING, A VALVE SEATENCOMPASSING SAID OUTLET PORT AND A MAGNETICALLY RESPONSIVE VALVE DISCMOVABLY POSITIONED IN SAID HOUSING BETWEEN SAID CHECK VALVE PORTS, WHICHVALVE DISC IS ATTRACTED TO SAID MAGNET AND ENGAGES WITH SAID SEAT TOCLOSE SAID OUTLET PORT DURING THE DISCHARGE STROKE OF SAID PISTON ANDDISENGAGES FROM SAID SEAT UNDER INLET FLUID PRESSURE INFLUENCE GREATERTHAN THE ATTRACTION OF SAID MAGNET TO OPEN SAID OUTLET PORT DURING THEINTAKE STROKE OF SAID PISTON, MEANS ADAPTED FOR MAINTAINING SAID PLUNGERMEANS IN SEALING CONTACT WITH SAID CYLINDER BORE DURING THE INTAKESTROKE OF SAID PISTON AND RESPONSIVE TO PRESSURE IN SAID CYLINDER BORETO PERMIT MOVEMENT OF SAID PLUNGER MEANS AWAY FROM THE END OF SAIDCYLINDER BORE AT A PRESELECTED PRESSURE, CONDUIT MEANS FOR PASSING FLUIDTO BE PUMPED TO SAID CHECK VALVE INLET PORT, AND FLUID DISCHARGE CONDUITMEANS COMMUNICATING WITH SAID CYLINDER BORE WHEN SAID FIRST OUTERSEATING SURFACE OF SAID PLUNGER MEANS IS DISENGAGED FROM SAID OUTER ENDOF SAID CYLINDER DURING THE DISCHARGE STROKE OF SAID PISTON.